1. Field of the Invention
The present invention relates generally to a combined mechanical and metallurgical connection. More specifically, the present invention relates to a threaded connection between two conduits in which an amorphous diffusion bond is also made at the threaded connection.
2. Description of the Related Arts
For purposes of this application, the present inventions will be described in contrast with mechanical and metallurgical connections that have been used in the oil and gas exploration and production industries. This background to which the present invention is compared and contrasted is not meant to limit the broad applicability of the inventions disclosed herein in any manner.
The oil and gas industry is challenged with finding more oil and gas to meet the ever-increasing worldwide demand. As one example, offshore drilling operations are commonly occurring today in 7,000 feet of water compared to an average of about 2,000 feet merely ten years ago. The cost to complete an offshore well increases exponentially with working depth and the tubular pipe required to complete a well remains the single largest expenditure for consumables.
It is common in the oil and gas exploration and production industries to use a threaded connection to join components, such as oilfield tubulars and pipes. Threaded tubular connections may be broadly categorized as coupling or non-coupling. Non-coupling connections typically cost less to manufacture and require less space downhole. However, such slim-hole connections typically are not as strong as the parent material, which they connect in terms of tensile, compressive and bending strength, or in the ability to seal against internal or external pressure. Various designs exist for threaded connections that meet established performance characteristics. For instance, threaded connections having substantially the same tensile strength as the parent material and substantially the same pressure capability as the parent material have been successfully designed. However, such connections always result in increased outside diameter compared to the parent conduit, which, therefore, requires a larger wellbore and concomitant increases in costs. Moreover, it is not uncommon for operators to require xe2x80x9cburst before leakxe2x80x9d performance from mechanical connections. Applicant is unaware of any mechanical connection having substantially the same geometry as the tubulars being joined and which also provides xe2x80x9cburst before leakxe2x80x9d performance.
When dimensional restrictions exist, threaded connections have been designed that are able to join sections of conduit with very little change in dimensions between the conduit and the connection. Either internally or externally flush connections are available as well as connections that are both internally and externally flush. However, these flush connections always have a lower strength than the parent material. The strength (tensile, compressive, fatigue and/or bending) of these connections can differ as much as 50% or more from that of the conduits being joined, which greatly limits their use.
In contrast to mechanical connections, such as threaded joints, there exist metallurgical connections, such as welded connections. Welded connections can also be finished to be externally flush and may be substantially flush on the internal dimension if proper welding procedures are used. The strength and pressure containment capability of these metallurgical connections can substantially match those of the conduit being joined. However, most welds cannot be performed in environments where a danger of explosive gases exists. Also, welding requires specially trained personnel and extensive non-destructive testing to insure that a proper weld is completed according to the welding specification. Further, traditional welding methods significantly (and often adversely) change the metallurgical, physical and corrosion resistance properties of the pipe in the weld and the heat affected zone. These changes cannot be fully removed or restored without full-scale heat treatment. Traditionally, welded connections have been limited to only the very upper portions of the string, which require the lowest strength and are, therefore, easier to weld.
One embodiment of the present invention is directed to a method of joining two components, where each component has a threaded end connection designed to mate with the other. An amount of ADB material is located on at least a portion of at least one of the threaded end connections. The threaded connections are joined with a predetermined amount of torque so that the ADB material is compressed between abutting surfaces. Heat is applied to the threaded connection adjacent the ADB material in an amount sufficient to cause diffusion bonding among the ADB material and the joined components.